In the past, a valve stem was manually mounted to a wheel with a stem-inserting tool. Such manual processes are expensive because of the labor and time involved. In addition, operations performed manually are subject to a relatively greater frequency of processing errors in comparison to robot-performed processes.
Several prior art patents disclose processes for mounting a valve stem to a wheel with programmable machines. For example, U.S. Pat. No. 6,481,083 teaches a valve stem assembly line that includes an input conveyor to supply wheels, a locator station positioned at the end of the input conveyor to locate the valve stem aperture defined by the wheel, and a robotic manipulator to grasp the wheel in the locator station and to move the wheel to the mounting station where a valve stem is inserted. U.S. Pat. No. 6,026,552 teaches a spinning device to spin the wheel, an optical sensor to locate the valve stem aperture while the wheel is spinning, and press fitting device that can slide relative to a wheel and insert a valve stem after the valve stem aperture has been located. U.S. Pat. No. 5,940,960 teaches and automatic valve stemming apparatus including a spinning device to spin the wheel, an optical sensor to locate the valve stem aperture, and a valve stem insertion tool to insert a valve stem after the valve stem aperture has been located.
A complication in the development of automated valve stem insertion tools has been the number of differently configured valve stems to be inserted in various wheels. The most common configuration of valve stem has a rubber exterior defining an annular notch for engaging the valve stem aperture. The degree of precision required in locating the valve stem aperture during assembly of the common rubber valve stem with a wheel is relatively less precise relative the assembly of some other types of valve stems because the common rubber valve stem can deform and resiliently return to its original shape. Another type of valve stem includes a tire pressure sensor and is known as a TPM valve stem. A TPM valve stem defines external threads which are inserted through the valve stem aperture and cooperate with a nut after insertion to maintain the position of the tire pressure sensor with respect to the wheel. The degree of precision required in locating the valve stem aperture during assembly of the TPM valve stem with a wheel is relatively more precise relative the assembly of the common rubber valve stem because the threads of the TPM valve stem can be irreparably damaged by contacting the valve stem aperture during assembly.
One of the areas of continuous development and research is the pursuit of flexible systems operable to receive and process several differently configured rims. Another area is the pursuit of less costly valve stem insertion devices. Costliness can be defined by the capital investment required for putting the valve stem insertion system on the factory floor as well as the operating cost associated with the system. In pursuit of these goals, it would be desirable to develop a valve stem insertion system having improved flexibility, cost and efficiency.